This invention is directed to a method of manufacturing a shelf, particularly a shelf adapted for utilization in a refrigerator of the type disclosed in the above-identified pending patent application. In the latter-identified pending patent application, several U.S. patents are noted in which a plate glass is bounded by a metal or plastic support frame. In U.S. Pat. No. 4,934,541 the plastic frame is made of an upper frame member and a lower frame member that cooperate to sandwich therebetween a periphery of a glass plate. A seal between the upper frame member and the glass plate prevents liquids from seeping between the glass plate and the upper frame member. In addition, the two frame members are ultrasonically welded together along a weld bead to unite the two frame members together and thus hold the glass shelf therebetween.
As noted in the above-identified pending patent application, a major problem with a multi-part plastic frame of the type disclosed in U.S. Pat. No. 4,934,541 is that the separate frame members must be separately manufactured, separately assembled, united with a glass panel and an associated seal, and thereafter unitized by the ultrasonic welding. The shelf of the pending application avoids these undesired characteristics through an in situ molding process by which a pair of shelf brackets are simultaneously interlockingly secured to side border portions of the plastic frame. In this manner the glass panel, the in situ molded plastic frame and the associated shelf brackets are essentially of a unitized construction which is extremely desirable from a manufacturing standpoint because of reduced costs and increased efficiencies. Also, from a use standpoint this construction is highly desirable because the integral homogeneous assembly of the shelf brackets, glass panel and frame is relatively strong and can be abused to a considerable extent absent deterioration and/or breakage. Additionally, the homogeneous nature of the overall in situ molding operation relative to the shelf brackets and the glass panel is aesthetically pleasing but, more importantly, this construction is highly sanitary because gaps and voids are nonexistent and, thus, spills or seepage can be readily and thoroughly cleaned with a minimum of effort.
A disadvantage of the in situ molding just described is that heretofore no provision has been made to maintain or assure proper alignment between the glass panel, the shelf brackets and the in situ injection molded frame during the high pressure injection and solidification of the latter. As molten plastic material is injected into an appropriate mold cavity under high pressure, there is a tendency for the glass panel to shift in the mold cavity because of differential forces acting against different portions of the glass panel. Due to the latter, the glass panel can undesirably shift in the mold cavity with the result that the injected plastic material, when solidified, is not properly oriented with respect to the peripheral edge of the glass panel and/or the shelf brackets associated therewith.